Control device



Dec. 22, 1959 HARRIS 2,917,939

CONTROL DEVICE Filed March 18, 1958 TIMER M0 TOR FRlCT/ON 6 I CLUTCH 23 GEAR TEETH OMITTED lllillllllllllllll 13 A 4 25 2 7 C21.

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United States Patent CONTROL DEVICE John L. Harris, Whitefish Bay, Wis.

Application March 18, 1958, Serial No. 722,226

6 Claims. (Cl. 74-435) This invention relates generally to timing devices.

The primary object of the invention is to provide a repeat cycle timer capable of giving an accurate short control cycle at infrequent intervals.

A further object is the provision of a timer which is driven through a cycle by a timer motor, and then disengaged from the timer motor so that a new cycle is delayed even though the timer motor continues to operate.

Other objects will appear from the following description and appended claims.

For a full description of the invention, reference is made to the accompanying drawings, in which:

Figure 1 illustrates schematically one form of the invention, and

Figure 2 is a view taken from line 22 of Figure 1.

Referring to Figure 1, reference character 1 indicates a timer motor unit which drives a pinion 2. This pinion drives a gear 3 which is carried by a cam shaft 4 which is freely supported in hearings in plates 5 and 6 (Fig. 2). This cam shaft carries a cam 7 upon which rides a cam follower 8, which is pivoted at 9, and operates a switch generally indicated as 10.

The switch 10 for illustrative purposes is shown as including cantilever spring blades 11, 12 and 13, sets of contacts 14, 15 and 16, and a spacer 17 between blades 12 and 13.

The pinion 2 also drives a gear train consisting of gears 18, 19, 20 and 21. The final gear 21 is rigidly supported on a shaft 22 which is freely supported between plates 5 and 6 (Fig. 2). Preferably a friction clutch is provided between gear 20 and its pinion 23, so that gear 21 may be turned manually by shaft 22.

The final gear 21 overlaps the gear 3, and causes a rearwardly extending pin 24 adapted to engage a forwardly extending pin 25 on gear 3. The gear 3 is also formed with a segment 26 in which the gear teeth have been omited. 1

Operation The parts are shown in the position assumed at the end of a cycle. The pinion has driven the gear 3 in a clockwise direction to the point where the teeth have disengaged, so that gear 3 and cam 7 are now stationary even though pinion 2 continues to rotate. The cam follower 8 is now on the top level of cam 7, and has closed switch contacts 11 and opened contacts 15 and 16.

The gear 21 is now being driven in a counterclockwise direction and eventually the pin 24 on this gear will come behind the pin 25 on gear 3, causing clockwise rotation of gear 3 and cam 7. This action will continue until the sloping portion 26 of cam 7 passes under the cam follower. At this time, the biasing action of spring switch blade 11 on the cam follower will cause the cam 7 and gear 3 to advance clockwise with snap action, thus operating the switch 10 and bringing the first tooth of the gear 3 into engagement with the pinion.

The sloping portion 27 of the cam, and the engaging POrtion 28 of the cam follower are proportioned relative to the first tooth of gear 3, to cause travel of this tooth far enough into the pinion as to be picked up by the pinion. In other words, this tooth is fed into the pinion far enough so that a tooth on the pinion comes in behind this first tooth and thus starts driving the gear.

The gear and cam now make a partial revolution in a clockwise direction. The first action of the cam on the follower is to close contacts 14 and open contacts 15. Later on in the cycle, the cam follower is raised more for opening contacts 16. Later the segment of omitted teeth 26 returns to the pinion thus causing the gear 3 and cam 7 to stop. The segment 26 is made wide enough so that gear 3 stops before pin 25 of the high speed gear 3 catches up with the pin 24 on the slow speed gear 21.

The shaft 22 may be used for rotating gear 21 independently of the timer motor 1. When this arrangement is used, it is recommended that pins 24 and 25 be arranged so that they cannot drive gear 3 far enough to re-engage the teeth. Thus, pins 24 and 25 should disengage before this happens, leaving it up to the cam follower to advance the cam and gear into engage ient.

In some cases in which the drive pinion is operating at relatively high speed, or is mounted in precision bearings, it is necessary to provide a strain relief between the pinion and gear to prevent possible jamming on engagement. In the present embodiment of the invention, this is accomplished by an elongated bearing hole 28 in back plate 5 through which shaft 4 extends. The cam follower 8 biases the cam downwardly, which in turn presses the gear 3 downwardly, toward the pinion 2. If the first tooth on gear 3 strikes a tooth on the pinion with a wedging action, the tooth on the pinion displaces the gear far enough to pass under. This displacement is permitted by the enlarged bearing hole.

From the foregoing, it will be apparent that the present invention provides a simple and positive cycling timer for obtaining extremely short and accurate cycles at times spaced far apart. This is achieved by the combination of a high speed cam which is stopped when its work is done, and restarted when the next cycle is desired.

While a preferred embodiment of the invention is disclosed, it will be apparent that many modifications can be made without departing from the spirit and scope of the invention as expressed in the following claims.

I claim:

1. In a timing device, a pinion, a timing motor for rotating said pinion, a gear arranged to mesh with said pinion for being driven thereby, said gear having a seg ment without teeth so that the gear disengages from the pinion at a predetermined point causing the gear to stop, means for advancing the gear from said point through said segment to cause re-engagement of the gear with said pinion, and spring loaded means for pressing said gear into engagement with said pinion until a tooth on the pinion is behind a tooth of the gear, so that the pinion resumes driving the gear.

2. In a timing device, a pinion, a timing motor for rotating said pinion, a gear arranged to mesh with said pinion for being driven thereby, said gear having a segment without teeth so that the gear disengages from the pinion at a predetermined point causing the gear to stop, means for advancing the gear from said point through said segment to cause re-engagement of the gear with said pinion, spring loaded means for pressing said gear into engagement with said pinion until a tooth on the pinion is behind a tooth of the gear, so that the pinion resumes driving the gear, and strain relief means between said gear and pinion for allowing an increased distance between centers thereof to prevent jamming of the gear and pinion on re-engagement.

3. In a timing device, a pinion, a timing motor for rotating said pinion, a gear arranged to mesh with said pinion for-being driven thereby, said gear having a segment without teeth so that the gear disengages from the pinion at a predetermined point causing the gear to stop, means for advancing the gear from said point through said segment to cause re-eri'gagernent of the gear with said pinion, spring loaded rneaiisffor pressing saidgear into engagement with said pinion until a'tooth on the pinion is b ehind a tooth of the gear, so that the pinion resumes driving the gear, and strain relief means between said gear and pinion for allowing an increased riistancebetween centers thereof to prevent jamming of the gear and pinion on re -engagernent. i 4. In a timing device a cam, a gear for rotating said canna pinion "for driving said gear, a timing motor for rotating the pinion, a cam follower biased against said c a mIs aidgear having a segment without teeth so that the gear disengages from the pinion at at predetermined point causing the geararid cam to stop, means for advancing the gear from said point for restarting the gear, said earn and follower being constructed and arranged to cause rotation of the gear and press the gear into en gagement with the pinion until a tooth on the pinion is behind a tooth on the gear, so that the pinion resumes driving the gear. 5. ,In a timing device, a cam, a gear for rotating said cam, a pinion for driving said gear, a timin g rno tor for rotating the pinion, a cam follower biased against said carn, said gear having a segment without teeth so t hat the gear disengages from the pinion at a predetermined point causing the gear and cam to stop, means for advancing the gear from said point for restarting the gear, said cam and follower being constructed and arranged to cause rotation of the gear and press the gear into engagement with the pinion until a tooth on the pinion is behind a tooth on the gear, so that the pinion resumes driving the gear, and strain relief means between said gear and pinion for allowing an increased distance be tween centers thereof to prevent jamming of the gear and pinion on re-eng agement.

6. In a timing device, a switch, a cam, a cam follower arranged to ride said cam and operate said switch, a gear for rotating said cam, a pinion for driving said gear, a timer motordriving said pinion, said gear having a segment without teeth so that the gear disengages the pinion at a predetermined point causing the gear and cam to stop, means for advancing the gear from said point, for restarting the gear, said cam and follower being constructed and arranged to cause rotation of the gear and press the gear into engagement with the pinion until a tooth on the pinion is behind a tooth on the gear, so that the pinion resumes driving the gear.

References Cited in the file of this patent UN E S AT S P E T$ 1,937,326 Pick Nov. 28, 1933 1,974,054 Popp Sept. 18, 1934 2,397,777 Colman Apr. 2, 1946 2,449,852 Jones Sept. 21, 1948 

